Delivery of agents with microneedles is receiving attention in recent years, because the same performance as delivering agents with syringes can be achieved without harming the skin and with less pain. Among microneedles, hollow microneedles, in particular, can widen the range of choices of agents to be provided in the hollow portion.
Other than hollow microneedles, there are, in general, self-dissolving-type needles in which the needle itself is made of a dissolvable agent, and coating-type needles in which the needle surface is coated with an agent. In both types, however, the amount of delivery of an agent (the amount of agent held) depends on the shape of the needle. In contrast, hollow-type needles are advantageous in that a large amount of agent can be delivered, irrespective of needle shape.
Such microneedles can be manufactured according to manufacturing methods disclosed in Patent Literature 1 or 2, for example. In the manufacturing method disclosed in Patent Literature 1, a resin body is arranged on an elastic body, and while heating the resin body from the back-surface side of the elastic body, a fine needle is caused to penetrate the resin body to manufacture a fine nozzle. Thus, there is no need to use a mold that includes a fine depression having an inverted shape of the outer shape of the nozzle, and a disposable fine nozzle can be manufactured from a resin.
Patent Literature 2 describes that a hollow microneedle array can be manufactured using a pre-formed mold.
Patent Literature 3 discloses a method for manufacturing microneedles by: arranging a base sheet so as to bridge rod-shaped protrusions; heating the entire base sheet; and causing the sheet to deform into the shape of the rod-shaped protrusions.
Further, delivery of agents with microneedles is receiving attention in recent years in the field of medical care or cosmetics. Microneedles can achieve the same performance as delivering agents with syringes without causing any pain by piercing only the outer layers of the skin. Among microneedles, microneedles having a through hole are particularly advantageous in that they can widen the range of choices of agents to be provided inside the microneedle. However, the use of a microneedle having a through hole, particularly in the field of medical care or cosmetics, calls for precision in microneedle height and precision of the through hole.
Microneedles having through holes can be manufactured according to the manufacturing methods disclosed in Patent Literatures 1 to 3, for example. Patent Literature 1 describes a method for manufacturing a fine nozzle by: arranging a resin body on an elastic body; and, while heating the resin body from the back-surface side of the elastic body, causing a fine needle to penetrate the resin body and causing the resin body to flow between the elastic body and the fine needle.
Patent Literature 2 describes a method wherein a hollow microneedle array is manufactured by molding by using a mold having a plurality of pre-formed depressions and a mold having a plurality of pre-formed projections, and inserting the projections into the respective depressions.
Patent Literature 4 describes a method for manufacturing a fine microneedle having a fine through hole by reproducing a fine microneedle on a substrate by thermal imprinting, and then forming a through hole by a short-pulse laser method.